The present invention relates to caster assemblies, and more particularly to caster assemblies of the type having a base for affixation to a support member and a wheel assembly supported by the base for rotational swiveling movement with respect to the base.
Caster assemblies are well known and widely used in many areas of everyday life and industry to support heavy objects for relatively easy lateral movement thereof on the wheels of such assemblies. Generally, the wheels of caster assemblies are carried by a swivel element for rotational swiveling movement about an axis perpendicular to the axis of rotation of the wheel whereby the wheel can readily align itself in an appropriate direction under the influence of the load borne thereby as it moves across the caster assembly. In industrial settings, a number of caster assemblies are often utilized in inverted orientation to form a conveyor path for the lateral transportation of heavy loads or objects. Thus, for example, trailers and loading apparatus having load support platforms comprising a plurality of inverted caster assemblies are utilized in the airline industry to facilitate the transportation and the loading of heavy cargo onto airplanes.
Although conventional caster assemblies of the industrial type are generally satisfactory for their various load bearing and transporting functions, such caster assemblies have proven to be susceptible to localized wear when utilized for bearing heavy loads and therefore generally have less than a desirable useful lifespan. Conventional caster assemblies typically utilize a ball bearing arrangement for mounting of the wheel assembly thereof on the base thereof in spaced relation to facilitate swiveling or rotational movement of the wheel assembly with respect to the base. Generally, the wheel of the wheel assembly is mounted in offset relation to the axis of rotation of the wheel assembly to better facilitate such swiveling movement when a load is placed on the wheel. However, as a result of this offset disposition of the wheel, a load imposed upon the wheel in any particular rotational disposition of the wheel assembly with respect to the base tends to be borne by the localized area of the ball bearing arrangement most closely adjacent (e.g. beneath) the wheel, thereby increasing the frictional contact between the respective components of the ball bearing arrangement in such localized area. Moreover, such conventional caster assemblies are typically constructed with the spacing between the facing surfaces of the bearing raceway extending concentrically about the axis of rotation of the wheel assembly at locations directly above and beneath the centers of the ball bearing elements. As a consequence, the aforesaid load imposed on the wheel will tend to be concentrated or localized at a few of the ball bearing elements directly at the point where the raceway spacing occurs and will tend to force the ball bearing elements into such spacing, thereby causing increased wear at the linear area of contact between the ball bearing elements and the raceway spacing while simultaneously increasing the frictional drag that must be overcome to permit the wheel assembly to swivel with respect to the base as the wheel assembly attempts to align itself in the direction of movement of the load being moved thereacross.
In contrast to the above, the present invention provides a caster assembly in which the raceway is uniquely formed and arranged such that the localized frictional forces created in the ball bearing arrangement upon loading of the wheel are applied to the surfaces of the ball bearings which are in contact with continuous portions of the ball bearing raceway to prevent the binding of the ball bearings in the raceway spacing between the base and the wheel assembly to reduce the degree of localized wear caused by such loading, and to reduce the forces necessary to cause desired swiveling of the wheel assembly as a load is moved thereacross.